CN109414997B

CN109414997B - Vehicle electrical system, charging station and method for transmitting electrical energy

Info

Publication number: CN109414997B
Application number: CN201780043246.9A
Authority: CN
Inventors: F.普法伊尔希夫特; P.布罗克霍夫; M.布吕尔; P-M.施魏策-贝尔贝里希; M.滕斯; E.席尔默
Original assignee: Continental Automotive GmbH
Current assignee: Vitesco Technologies GmbH
Priority date: 2016-07-11
Filing date: 2017-06-27
Publication date: 2022-03-29
Anticipated expiration: 2037-06-27
Also published as: US11097626B2; EP3481664B1; EP3481664A1; DE102016212543A1; KR20190026845A; US20190210475A1; CN109414997A; EP4164087A1; WO2018010948A1

Abstract

A vehicle electrical system (FB) is described, which has an electrical energy store (10, 110), a direct-current voltage converter (DCDC, 20) and direct-current transmission terminals (DC +, DC-). The direct current transmission terminals (DC +, DC-) are connected to the Energy Store (ES) via the direct current voltage converter (DCDC; 20). The vehicle electrical system also has a jumper switch (40, 40 lambda) which switchably connects the electrical energy store (10, 110) to a direct voltage transmission terminal (DC +, DC-). Furthermore, a method, a charging system, a charging station and another vehicle electrical system are described.

Description

Vehicle electrical system, charging station and method for transmitting electrical energy

Background

Motor vehicles with an electric drive, i.e. electric vehicles and hybrid vehicles, comprise an electrical energy store for supplying the electric drive with electrical energy. Electric vehicles and plug-in hybrid vehicles are equipped with terminals by means of which energy can be transmitted from a stationary supply network (local or public) to an energy store in order to charge the energy store. If necessary, the vehicle is also equipped for feeding back energy to the supply grid.

In order to transmit electrical energy between the supply grid and the vehicle, power electronics are required, in particular for controlling the energy transmission. In particular in the case of high charging powers, expensive components are required, for example, in order to charge particularly quickly.

Disclosure of Invention

The object of the present invention is to indicate a possibility with which the complexity of such components can be reduced or with which high charging powers can also be achieved with reduced complexity for the power electronics.

This object is achieved by the subject matter of the independent claims. Further advantages, features, embodiments and characteristics emerge from the dependent claims and from the description and the figures.

It proposes: if a voltage suitable for direct supply to the energy store (i.e. not exceeding the load limit of the energy store) is applied to the inverter during charging, a direct-current voltage converter (hereinafter DCDC converter) connecting the electrical energy store to a direct-current transmission connection (hereinafter DC plug-in) is connected across the vehicle electrical system. In other words, for example in the case of an excessively low state of charge or an excessively low voltage of the energy store, power is transmitted via the DCDC converter, in particular in order to adapt the voltage of the DC plug-in to the (lower) voltage of the energy store. If the voltage or the state of charge of the energy store is sufficiently adapted to the voltage at the DC link (which is derived, for example, by rectifying the alternating voltage of the supply grid), the charging energy is no longer transmitted via the DCDC converter but directly from the DC link to the battery. This becomes possible when the DCDC converter is closed by a cross-over, i.e. a cross-over switch (in parallel with the DCDC converter). This may also apply to charging stations.

Thus, for example, a direct-current voltage converter (DCDC converter) used in traction can also be used for charging within the vehicle. If the traction power is low relative to the charging power, the DCDC converter need not be designed according to the higher charging power. Instead, in order to achieve a high charging power, the jumper switch is closed (bypass switch in the vehicle and/or in the charging station). This can be implemented in a range in which the plug voltage substantially corresponds to the energy store voltage, so that if the switch is closed, no high switching currents or energy store overload occur. The DCDC converter in the charging station can also be used first only to increase the voltage output by the charging station until the deviation from the energy store voltage falls below a predetermined value. From this point on, the switch of the DCDC converter across the charging station is closed and charging at higher power is possible. In this case, the DCDC converter of the charging station can also be designed for comparatively low powers, since the rapid charging process is carried out with the switch closed. The switch of the DCDC converter across the vehicle onboard network is referred to as a cross-over switch. For the sake of distinction, the switches across the DCDC converter are synonymously denoted, i.e. referred to as bypass switches.

The concept of the process described herein is represented by a method for transferring electrical energy. Energy is transferred between an energy store of the vehicle electrical system and the charging station via a direct-current voltage converter of the vehicle electrical system. Alternatively, energy is transferred between the energy store and the charging station via a fixed dc voltage converter of the charging station. Furthermore, energy can be transferred via two direct voltage converters.

If the voltage at the voltage converter concerned is below a predetermined value, the DC voltage converter or the DC voltage converter is connected. The voltage difference relates in particular to the no-load voltage of the energy store to which the dc voltage converter is connected directly (in the case of a vehicle-side dc voltage converter) or indirectly (in the case of a charging station-side dc voltage converter).

The dc voltage converter or the dc voltage converters are connected if the voltage difference between the voltage applied to the side of the relevant voltage converter facing away from the energy store and the no-load voltage of the energy store is below a predetermined value. To determine whether the voltage difference is below a predetermined value, the absolute value of the voltage difference can be compared with the value. In particular, the voltage difference corresponds to the no-load voltage of the energy store minus the voltage applied to the voltage converter as mentioned. The no-load voltage may be measured by a voltage measurement in case the current is substantially zero, a voltage measurement and an associated current measurement in case of different currents, an interrogation by a battery management unit, etc.

In particular, the energy is transmitted via an inverter of the charging station, which is connected between the stationary ac power supply system and the dc voltage converter of the charging station. The energy may be transmitted towards the vehicle onboard electrical system (charging) or away from the vehicle onboard electrical system (feedback). Preferably, the voltage is first transmitted until the voltage difference across the converter to be bridged later (in particular with respect to the no-load voltage of the energy store) falls below a predetermined value, wherein the value corresponds to a switching power which is not greater than the maximum permissible switching power of the switch by which the crossover is to be bridged. The voltage state of the energy store can be transmitted as a data signal from the vehicle electrical system to the charging station, wherein the voltage state can be characterized by the no-load voltage or the terminal voltage (or also by the charging state) of the energy store. Furthermore, a fault signal can be transmitted from the vehicle electrical system to the charging station, which fault signal terminates the voltage span present there, independently of the voltage state of the converter of the charging station. During the strapping, the converter or the converter is preferably inactive.

Furthermore, a vehicle electrical system is described, which has an electrical energy store, a direct-current voltage converter (DCDC converter) and a direct-current transmission terminal (DC plug-in). The DC plug-in is connected with the energy store via a DCDC converter. The DCDC converter connects the DC plug with the energy storage.

The vehicle electrical system has a jumper switch. The jumper switch switchably connects the energy store to the DC link. In particular, the jumper switch is connected in parallel with the DCDC converter and/or in parallel with a side of the DCDC converter. The cross-over switch connects two sides of the DCDC converter, and performs voltage conversion between the two sides. In other words, the cross-over switch (in a switchable manner) crosses over the DCDC converter.

A control unit is provided which actuates the jumper switch into the closed state if a direct connection between the DC plug and the energy store would result in an energy flow which does not exceed the load limit of the energy store. Another consideration is that the closing of the jumper switch only closes if it would result in a load (caused by the switching current) of the jumper switch that is below a predefined switching current value. In particular, the jumper switch is closed only when the voltage difference over the DCDC converter (i.e. the difference between the voltage over the energy storage, in particular its no-load voltage, and the voltage over the DC plug-in) is substantially zero. The load of the energy store or of the jumper switch (when closed) can thus be adapted when determining the switching state of the jumper switch. In particular, the bridging switch is closed only if a direct connection between the DC plug and the energy store would result in an energy flow that does not exceed the load limit of the energy store.

The estimation of whether the load limit is reached is preferably based on the voltage difference between the voltage of the energy storage and the voltage on the DC card. This corresponds to the voltage over the DCDC converter, i.e. the voltage difference between the sides of the DCDC converter. This is in particular dependent on the no-load voltage of the energy store, which is connected directly or indirectly to one side of the respective DCDC converter. If this relates to the terminal voltage, the current flowing is considered as follows: the switching power or the switching current across the switch is lower than a predetermined switching power or lower than a predetermined maximum switching current. If the switching power or the switching current is less than a predetermined value, it is assumed that: no load limit is exceeded and/or no maximum switch current across the switch is exceeded. Otherwise, assume: the load limit will be exceeded by closing the cross-over switch or by closing the cross-over switch. The load limit may be related to a cross-over switch or to an energy store.

The charging process can therefore be carried out by means of the vehicle onboard power supply system as follows: if the deviation of the voltage state of the energy store from the voltage at the DC plug-in is greater than a predefined (permissible) deviation value, the energy store is charged via the DCDC converter. Furthermore, charging of the energy store via the jumper (or closing of the jumper) is provided if the deviation between the variables mentioned is not greater than a predefined value. In particular, if the energy store approximately has a dc voltage (terminal voltage or no-load voltage) which is obtained by rectifying the ac voltage, the jumper switch is closed.

If a fixed dc voltage converter is located in the charging station, it can also be bridged if this does not result in the load limit of the energy store or of the switches used for carrying out the bridge connection being exceeded.

When charging the energy store via the jumper switch, the energy store is preferably charged at a higher power than when charging the energy store via the DCDC converter. The two powers may have a ratio of 2:1, 3:1, or 4: 1. In other words, the DCDC converter may be designed for a lower power than the maximum charging power of the energy store, for example for a power which is not more than 10%, 15%, 20% or not more than 40%, 50% or 60% of the maximum charging power of the inverter or the energy store within the charging station. This design of the power can be adapted to the DCDC converter within the onboard power supply system, the DCDC converter within the charging station, or both. For a DCDC converter within the vehicle electrical system, different values than for a DCDC converter within the charging station may apply.

The DCDC converter of the onboard power supply system converter may have a nominal power which is lower than the maximum charging power of the energy store. The DCDC converter of the onboard power supply system converter may have a nominal power of no more than 10%, 15%, 20% or no more than 40%, 50% or 60% of the maximum charging power of the energy store.

The DCDC converter of the charging station may have a nominal power which is lower than the nominal power of the inverter of the charging station. The DCDC converter of the charging station may have a nominal power of not more than 10%, 15%, 20% or not more than 40%, 50% or 60% of the nominal power of the inverter of the charging station.

The jumper switch is designed for a power or current which corresponds at least to the maximum power or maximum current of the energy store, or in particular exceeds said maximum power or maximum current by at least 20% or at least 40%. This applies for the non-switching state, i.e. for the continuous load across the switch and not for the switching power.

An inverter may be provided in the vehicle electrical system, which inverter connects the electric machine to the DCDC converter. Thus, in driving operation, the electric machine can be supplied with energy from the energy store via the DCDC converter and the inverter (in this order).

The DCDC converter is in particular a boost converter, for example a synchronous converter. The energy store is in particular a high-voltage store (i.e. having a nominal voltage of at least 60V, 120V, 240V, 360V or 380V), for example a high-voltage battery. The energy store is in particular a lithium-based battery (for example a lithium-ion battery). The energy store is preferably a battery or in other words a stack of primary cells (in particular secondary cells) which are connected to one another as energy store cells of the energy store. The electrical energy store is in particular a battery, for example a lithium-based battery (for example a lithium-ion battery). The electrical energy store may be a traction battery. The energy store may have a nominal voltage of 40-60V, in particular 48V, and in particular may have a nominal voltage of more than 100 volts, in particular at least 200V or 300V, for example 350-420V. The electric machine is in particular a three-phase electric machine. The motor is multi-phase, in particular three-phase or six-phase. The electric machine may be a separately excited or a permanently excited electric machine. It can be provided that: the motor is provided with a star point; other configurations provide a triangular configuration of the motor. The positive busbar can be connected to the phase current terminals (of the inverter) via a star point.

The dc transmission terminal may comprise a plug-in Inlet (plug-Inlet), i.e. an electromechanical plug connection element which may be mounted in a housing of the vehicle. The dc transmission terminal is set up for connection with a charging plug (or more generally: a connection plug).

A control unit may be provided which actuates the bridging switch. Furthermore, the control unit or a further control unit which controls the dc voltage converter and, if appropriate, the inverter can be provided. The control unit is operatively connected to the jumper switch and in particular to the dc voltage converter. In the inverter mode of the control unit, the inverter is controlled to generate phase voltages from the direct voltage of the energy store, said phase voltages being applied to the phase terminals. In an (optional) recovery mode, the control unit commands the inverter to generate a charging voltage on the energy store from the phase voltages on the phase terminals. In an (optional) feedback mode, the control unit actuates the inverter to generate a feedback voltage at the dc link from a voltage present at an energy store of the vehicle electrical system.

In the charging mode, the control unit actuates the DCDC converter in order to generate a charging voltage on the energy store from a voltage applied to the direct current transmission terminals. The control unit performs this when the cross-over switch is open. In the closed state, the control unit does not control the DCDC converter or controls the DCDC converter such that no current flows through the DCDC converter (for example by opening all switches of the DCDC converter).

The DCDC converter has a semiconductor switch or a switching element. These semiconductor switches or switching elements are preferably transistors, in particular field effect or bipolar transistors, for example MOSFETs or IGBTs.

The jumper switch may be located in particular in a positive busbar of the vehicle electrical system. In this case, the DCDC converter and the energy store have a common ground (so that the jumper switch switches or jumpers in the positive busbar).

The DC plug-in preferably has a negative potential, which is connected to the negative terminal of the DCDC converter. The dc voltage transmission terminal may have a positive potential, which is connected with the positive terminal of the dc voltage converter. The jumper switch preferably connects the positive terminal of the DCDC converter with the positive pole of the electrical energy store.

As mentioned, the vehicle electrical system also has a control unit. The control unit is operatively connected to the dc voltage converter and/or to the jumper switch. The control unit is furthermore connected to an energy store, in particular in order to obtain signals, for example measurement signals, status signals or signals derived therefrom, from the energy store. The control unit is set up to determine the voltage of the energy store. This voltage represents in particular: whether the energy store is in a state in which a supply via the jumper switch will not lead to an overload of the energy store or of the jumper switch. The deviation is a measure of which power or which current or which charging voltage can be supplied to the energy store, and in particular of how far away from the operating point the load limit (in terms of current, voltage or power) of the energy store or the load limit of the jumper switch (in particular the maximum switch current) is to be derived if the DC plug-in is to be connected directly to the energy store via the jumper switch. The deviation can be specified as a margin, which specifies the distance from the load limit of the energy store.

The control unit is also connected to the dc transmission terminal and is set up to determine its voltage. The control unit may have a voltage measuring unit or a data input for this purpose, via which the voltage is received by the control unit as a value from a battery management unit of the energy store.

The control unit is also designed to determine a deviation between the voltage state of the energy store and the voltage of the dc transmission terminal. For this purpose, the control unit may have a difference-forming device or a calculator for this purpose. Furthermore, the control unit is designed to set the jumper switch in the closed state (for example by outputting a corresponding control signal) if the deviation is not greater than a predefined value. The control unit is set up to place the bridging switch in the open state if the deviation is greater than a predetermined value. The value may decrease from a predetermined temperature value as the temperature increases, may decrease as the temperature falls below a predetermined further temperature value, may decrease as aging increases, may decrease as the internal resistance decreases, or may be constant. Aging, internal resistance and temperature are associated with the energy store or with the jumper switch or bypass switch.

The control unit is also set up to determine the no-load voltage from the terminal voltage of the energy store (for example, using the measured energy store current) in order to use this variable as a voltage state. Furthermore, the control unit can be set up to determine the voltage state (in the sense of a no-load voltage) from the charge state and/or the aging state (obtained by the battery management unit of the energy store). Based on this estimate or prediction, the jumper switch is actuated, in particular such that the load limit or the current absorption capacity of the energy store is not exceeded.

The voltage state may be represented by a value representing a state of charge, a terminal voltage, a no-load voltage, or a maximum charging current. The control unit is designed to actuate the jumper switch as a function of this value.

Furthermore, the control unit (of the vehicle electrical system) can be set up to transmit the current value, the voltage value or the power value as a setpoint value if the current absorption capacity exceeds a threshold value, in particular to a control unit of a charging station, which is set up to output a current, a voltage or a power corresponding to the setpoint value on a DC plug-in. The control unit (of the vehicle electrical system) can be set up to output the current value, the voltage value or the power value as a setpoint value to the dc voltage converter without exceeding a threshold current absorption capacity. In other words, the control unit is designed to control the DCDC converter of the vehicle electrical system in order to set the charging power, the charging current and/or the charging voltage if the current absorption capacity of the energy store is not sufficient (i.e. if a threshold value is not exceeded or if a load limit is to be exceeded if the jumper switch is closed), and is also designed to output a control signal (i.e. a setpoint value), which can be received by the fixed control unit and used as the setpoint value. With the closing of the jumper switch, the control unit therefore converts the actuation of the (vehicle-side) DCDC converter to the actuation of the charging station or its converter as a function of the setpoint value. The control unit of the vehicle onboard power supply system is set up to actuate the switches of the DCDC converter of the vehicle onboard power supply system as a function of the open state when the bridging switch is closed (and thus bridges the DCDC converter of the vehicle onboard power supply system).

The control unit can furthermore have a transmission unit. The transmitting unit is set up to transmit the voltage state, the deviation of the energy store or the switching state of a jumper switch of the vehicle electrical system, in particular to a receiving unit of the charging station.

It can be provided that: the predefined value is not greater than 10%, 5%, 2% or 1% of the nominal voltage of the energy store 10.

The control unit (of the vehicle electrical system) is in particular operatively connected to the dc voltage converter. The control unit is set up to place the dc voltage converter in an inactive state when the jumper switch is closed (for example, using an open switching element of the DCDC converter). The control unit is also set up to set the DCDC converter in the active state when the jumper switch is open. This can be done by directly actuating the DCDC converter by means of the control unit or by actuating a driver circuit or an actuating circuit which generates the switching signals for the switching elements of the DCDC converter.

Furthermore, a charging system (in the sense of a device) is described. The charging system includes a mobile unit to be charged (a vehicle having a vehicle onboard power grid as described herein) and a charging station. The charging station has a (fixed) inverter and furthermore a (fixed) dc voltage charging terminal and a (fixed) dc voltage converter. A fixed switch is connected in parallel with the fixed dc voltage converter. The switch is designed to be actuated by a signal transmitted by the vehicle electrical system, or to be actuated according to a setpoint value transmitted by the vehicle electrical system. Furthermore, provision can be made for: the (fixed) inverter and/or the (fixed) dc voltage converter are designed to operate according to a setpoint value transmitted by the vehicle electrical system. Thus, a fixed dc voltage converter can also be bridged if the direct transmission of the rectified ac voltage of the supply grid would not lead to an overload of the energy store. If this would lead to an overload of the energy store (of the vehicle onboard power supply system), no bridging takes place on the charging station side. Instead of an inverter, a (controlled or uncontrolled) rectifier can also be used in the charging station.

The charging station may have a receiving unit which is set up to receive a voltage state, a deviation of the energy store or a switching state of a jumper switch of the vehicle electrical system, for example, by receiving a signal transmitted by a control unit of the vehicle electrical system or by a transmitting unit of the control unit. The control unit may be connected downstream of the receiving unit or the receiving unit may form part of the control unit. The control unit is set up to obtain relevant data (voltage state, deviation or/and switching state) from the receiving unit.

The stationary control unit (i.e. the control unit of the charging station) is in particular connected to the connection point between the stationary dc voltage charging terminal and the stationary inverter. The control unit is designed to determine the voltage at the connection point.

The fixed control unit is preferably also designed to determine a deviation between the voltage state of the energy store and the voltage of the connection point. The fixed control unit is set up to set the fixed bypass switch in the closed state if the deviation is not greater than a predefined value. The fixed control unit is set up to place the jumper switch in the open state if the deviation is greater than a predefined value. As explained above, this value can also depend on the aging, temperature and/or internal resistance of the energy store or bypass switch, or on the charge state of the energy store.

As mentioned, the vehicle onboard electrical system may have ac transmission terminals. The ac transmission terminal can be connected to an inverter (or to the ac side thereof) of the vehicle electrical system via a winding of the electric machine. The ac transmission terminal may be multi-phase, e.g. three-phase. The DC side of the inverter of the vehicle electrical system is connected to the DCDC converter and to a DC plug-in of the vehicle electrical system.

The vehicle electrical system is in particular an electrical system of a plug-in hybrid motor vehicle or electric vehicle.

Furthermore, a charging station, in particular a charging station that can be used in a charging system, is described. The charging station is equipped with a stationary inverter, stationary dc voltage charging terminals and a stationary dc voltage converter. The dc voltage converter connects the inverter to a fixed dc voltage charging terminal. The (fixed) bypass switch is connected in parallel with the fixed dc voltage converter. The bypass switch is connected (as long as it is in the closed state) across the fixed direct voltage converter (i.e. the DCDC converter of the charging station). The charging station has a fixed control unit. The control unit is connected in a controlled manner to the bypass switch.

The charging station may have a receiving unit. The receiving unit can be set up to receive a voltage state of an energy store of the vehicle electrical system connected to the charging station, a switching command or a switching state of a jumper switch of the (connected) vehicle electrical system. The receiving unit is preferably connected to a stationary control unit. The control unit is designed in particular to set the bypass switch in the closed state if the voltage state of the energy store deviates by no more than a predefined value from the voltage present between the inverter and the fixed DC voltage converter, if a switching command for closing the bypass switch is present, or if the switching state of a jumper switch (40) of the vehicle electrical system is closed. "or" in this case associates only the individual characteristics of the event dependency, not the event itself. Furthermore, the control unit is set up to actuate the fixed bypass switch as a function of the open switching state.

In addition, a vehicle electrical system is described, which has an electrical energy store, a direct-current voltage converter (also referred to as a DCDC converter) and an inverter. The energy store, the direct voltage converter and the inverter preferably correspond to the energy store, the direct voltage converter and the inverter mentioned above and below. The inverter is connected to the energy store via a dc voltage converter. The motor (motor) is connected downstream of the inverter. The electric machine is connected via an inverter either directly to the energy store via a jumper switch described below or indirectly via a DCDC converter. The vehicle electrical system also has a jumper switch, which switchably connects the electrical energy store to the inverter. The jumper switch preferably corresponds to the jumper switch mentioned above and below, which in the same way bridges the sides of the DCDC converter. In particular, the jumper switch is connected in parallel with the DCDC converter and/or in parallel with a side of the DCDC converter. The jumper switch connects both sides of the DCDC converter, and performs voltage conversion between the both sides. In other words, the cross-over switch (in a switchable manner) crosses over the DCDC converter. The vehicle electrical system has, in particular, a control unit. The control unit can be operatively connected to the jumper switch and in particular also to the DCDC converter. The control unit is designed to receive the boost signal. The boost signal represents a particularly high power requirement for the inverter. The boost signal may relate to a traction state in which the inverter outputs alternating current power (Wechselleistung). The boost signal may furthermore relate to a recovery state (in which the inverter absorbs ac power). The control unit is preferably set up to set the jumper switch in the closed state if a boost signal is present and to set the jumper switch in the open state if no boost signal is present. The inverter is directly powered by the energy store via the closed cross-over switch. Thus, the power is not limited by the maximum power of the DCDC converter (given by the design of the DCDC converter). The nominal power of the inverter is preferably higher than the nominal power of the DCDC converter. The inverter preferably has a nominal power of at least 150%, 200%, 400% or 600% of the nominal power of the DCDC converter. The control unit mentioned in this paragraph may correspond to the control unit mentioned in the following and preceding paragraphs. The control unit can be set up to place the jumper switch in the closed state if a boost signal is present or if the deviation between the voltage state of the energy store and the voltage of the dc link is not greater than a predefined value. The control unit may be set up to place the jumper switch in the open state if no boost signal is present or if the deviation between the voltage state of the energy store and the voltage of the dc link is greater than a predefined value. Thus, the cross-over switch can be used for a variety of functions: on the one hand, for directly coupling the energy store to the inverter when particularly high traction power or recovery power is required and, on the other hand, for directly coupling the energy store to the dc voltage transmission connection when the voltage state of the energy store (in particular the no-load voltage) deviates by no more than a predetermined value from the voltage of the dc voltage transmission connection. In both cases, the DCDC converter is bridged by a jumper switch in order to connect the energy store directly to a power source (charging station or electric motor as generator) or to a power sink (Leistungssenke) (charging station or electric motor as drive during the feedback). Otherwise, a DCDC converter is connected upstream of the energy store for voltage adaptation.

Drawings

Fig. 1, 2 and 3 serve to explain the devices and methods described here in more detail and to show (in particular) an exemplary vehicle onboard power supply system and charging station.

Detailed Description

Fig. 1 and 2 each show an embodiment of a vehicle electrical system FB having an

energy store

10 or 110 and an electric machine EM or EM' which are connected to one another via an inverter 30 or WR. The direct current transmission terminals DC +, DC- ("DC plug-in") have a positive busbar DC + and a negative busbar DC-. The DCDC converter 20 or DCDC connects the DC plug-in with the

energy storage

10 or 110.

Fig. 1 shows a control unit CT which receives at least one signal from the energy store 10 (which characterizes the current absorption capacity of the energy store), see the arrow pointing to CT. The control unit CT is operatively connected to the DCDC converter 20 and to the jumper switch 40.

If the jumper switch 40 is open, the energy is transferred via the DC plug-in DC +, DC-via the path I to the DCDC converter 20, which converts the energy, in particular by increasing the voltage or generally adapting the voltage to the (current) voltage of the energy store 10. If the jumper switch 40 is closed, energy is transferred via the DC plug-in DC +, DC-via path II and via the jumper switch 40 (which serves as a bypass for the DCDC converter 20), which converts the energy, to the energy storage 10. Path I is selected if the deviation of the voltage between the energy store 10 and the direct voltage terminals DC +, DC-is above a predetermined value. If the voltages are sufficiently equalized (i.e., the deviation does not exceed this value), charging is not done indirectly via the DCDC converter 20, but directly via the cross-over switch 40.

The electric machine EM is connected to the DCDC converter 20 via an inverter 30, which is supplied with power by the inverter 30, for example, during driving operation (not shown), which in turn receives the voltage of the energy store 10, which is increased by the DCDC converter. The charging operation is represented by paths I and II. If the DCDC converter is necessary for voltage adaptation, path I is used at the beginning of the charging, since the voltage of the energy store and the voltage on the DC plug-in are too different. If the DCDC converter is no longer necessary for voltage adaptation, path II is used in the subsequent phase of charging, since the voltage of the energy store and the voltage on the DC plug-in are sufficiently close to one another in order to avoid overloading of the energy store. Path II may represent power that is at least two, three, or four times the power of path I. Accordingly, the DCDC converter may be designed for a power that is only a fraction (no more than 50%, 30%, or 20%, or no more than 10%) of the power from which the cross-over switch is designed. The processing described here can be used even in the case of feedback, in that: if the deviation of the voltage of the energy store 10 from the voltage at the DC-plug DC +, DC-is greater than a predetermined value, power is fed back via path I, and if the deviation of the voltage between the energy store 10 and the DC-plug DC +, DC-does not exceed this value, power is fed back via path II.

In order to determine the voltage at the energy store 10, the control unit CT can be set up to determine the voltage by measurement at the energy store. Furthermore, the voltage across the energy store 10 may be determined by the control unit CT by receiving voltage values from the battery management unit 12 of the energy store 10. This is illustrated by means of a dashed arrow directed downwards towards the control unit CT.

The control unit CT can have a transmitting unit S for transmitting the voltage state of the energy store 10 or the switching state of the jumper switch 40, for example to a charging station. This is illustrated by the dashed arrow directed downwards away from the control unit CT.

Fig. 2 shows a vehicle electrical system FB connected to a charging station Inf.

In the vehicle electrical system FB of fig. 2, the inverter WR is connected to the direct-current voltage converter DCDC via a positive input current terminal EA1 of the inverter WR and a negative input current terminal EA2 of the inverter WR. An intermediate circuit capacitor 112 is connected in parallel to the input current terminals EA1, EA 2. The inverter WR includes three bridges B1-B3. The potential or contact of the DC transmission terminal DC +, DC-, in particular the positive busbar DC +, is connected to the DC voltage converter DCDC and, in addition, to the positive input current terminal EA1 of the inverter WR.

Fig. 2 shows an inverter with a full bridge B1-B3, which is also referred to as a double pulse bridge, since each of the two half waves of a full wave is transmitted via one of the two switches of the respective bridge. In fig. 2, the B6C bridge circuit created by each bridge B1-3 is referred to as BnC, where n is a placeholder for the number of switching elements (here: 3 x 2 = 6). An inverter WR1 is shown in fig. 2, implemented as a multi-phase full wave bridge circuit. The inverter WR is a B6C bridge circuit with an intermediate circuit capacitor 112.

The dashed line marks the interface between the vehicle onboard power supply system and the stationary charging station Inf.

In fig. 2, the inverter WR is indirectly connected to the DC link DC +, DC-via the DC voltage converter DCDC via the electric machine EM. Voltage adaptation is thereby possible, in particular overlapping voltage bands of the electric machine EM and/or the inverter WR on the one hand and the energy store 110 on the other hand. The energy store 110 has a disconnection switch T in addition to a storage cell (spellerzellen). The dc voltage converter DCDC has two series switches Z1, Z2, and a series inductance L is connected to the connection point thereof, which connects the series switches Z1, Z2 to the intermediate circuit capacitor K of the dc voltage converter DCDC. The connection point between the switches Z1 and Z2 is connected to the positive pole + of the energy store 110 via an inductance L. The intermediate circuit capacitor K is also connected to the negative input current terminal EA 2; the positive input current terminal EA1 is connected to the intermediate circuit capacitor K via a switch Z1 and an inductance. In particular, a voltage which is lower than the operating voltage of the energy store 110 (for example approximately 800V) at the DC voltage terminals DC +, DC "is made possible by the DC voltage converter DCDC which is connected in between.

The electric machine EM' of fig. 2 comprises a winding system with three phases L1-L3 and with a center tap in each of the windings, whereby each winding is divided in half. The division into two halves does not necessarily have to be an equally long winding section, but depends in particular on the requirements placed on the filter EMC. A filter EMC with capacitors Cx and Cy is connected to the intermediate tap and to the winding ends opposite the inverter WR2 or its phase terminals PS 1-3. Since the capacitors Cx and Cy interact with the windings of the electrical machine, the windings or sections thereof can be part of the filter EMC in the functional view. The filter EMC is furthermore connected to the neutral conductor N. The capacitors Cx, Cy of fig. 2 and thus the filter EMC (due to the series switch) can be separated from the electric machine EM'.

The switching device SB connects the electric machine EM' or its phases L1-L3 with the alternating current terminal AC of the vehicle onboard network FB. The switching device SB comprises two switching elements or disconnecting switches (auftrennschelter) which connect the phases to one another in a controlled manner, in particular in order to form a star point or, preferably, not completely release it. In particular, the switching device may have only one disconnector, which connects the two windings in a controlled manner. The remaining one or more windings are preferably connected with the other windings, either permanently or via a direct connection. In other words, the disconnection switch or the disconnection switches are connected such that an incomplete (star or triangle) configuration results in the case of opening of one or more switches, or a complete de-configuration (by separating all winding ends from one another), wherein the disconnection switch ensures that no direct current flows through all windings. The control unit CT' can be operatively connected to the switching device SB in order to implement the aforementioned in the charging mode and/or the feedback mode and in order to connect all windings to each other in the motor mode or in the generator mode (for example in order to establish a symmetrical or complete configuration). In addition, in the charging mode and/or the feedback mode, it can be provided that the control device actuates the switching device SB to transmit a direct current via different windings and/or winding subsets. The control device is designed for such a manipulation. Thereby more uniformly generating waste heat in the motor.

The switching device SB may furthermore comprise one disconnector for each phase, wherein the disconnector is connected between the electric machine EM' and the alternating current terminal AC.

The interface (shown in dashed lines) is implemented by an electromechanical interface which forms a first plug connector STE1 on the vehicle electrical system FB side and a plug connector STE2 complementary thereto on the infrastructure Inf side. The first plug connector is in particular part of the plug-in inlet. The second plug connector STE2 is fixed, in particular at the end of the charging cable of the charging station Inf. On the charging station side, a current source SQ for the alternating current is provided, which current source is intended to represent the access to the alternating current supply network. Three phases L1-L3 are formed, as well as a neutral conductor N and a guard conductor SL. These have counterparts on the vehicle side (entsprechung) which have the same name for the sake of greater clarity.

The DC terminals DCA-stat of the charging station are connected via a DC voltage converter DC-stat of the charging station to an inverter or rectifier Inv-stat of the charging station Inf, which is in turn connected to the ac power supply network. Alternatively, a direct voltage source can be provided to which the direct voltage converter DC-stat is connected. The direct voltage converter DC-stat is connected in parallel with a switch 42, which in the closed state is connected across the direct voltage converter DC-stat. Depending on whether the closed state would lead to an overload of the DCDC converter DCDC or of the energy store 110 of the vehicle electrical system (so that the switch 42 remains open) or would not lead to an overload of the DCDC converter DCDC or of the energy store 110 of the vehicle electrical system (so that the switch 42 can be closed), the control unit CT' (vehicle electrical system FB) also actuates this switch 42.

The control unit CT 'of the vehicle electrical system is set up to transmit the voltage state or the switching state of the energy store 110 or of the jumper switch 40' to the charging station Inf. This is illustrated by the curved dashed arrow.

Fig. 3 shows a charging station Inf with an inverter Inv-stat, DC voltage charging terminals DCA-stat and a DC voltage converter DC-stat. The inverter Inv-stat is connected to the fixed DC voltage charging terminals DCA-stat via the DC voltage converter DC-stat. The fixed bypass switch 42 is connected in parallel or in a cross-over connection to the fixed DC voltage converter DC-stat. Fig. 3 shows in particular the charging station shown in fig. 2.

The charging station Inf has a control unit CT-stat. Which is connected in a controlled manner to the bypass switch 42. The control unit CT-stat has a receiving unit E. The receiving unit is set up to receive, for example, a voltage state (of an energy store of the vehicle electrical system) or a switching state (of a jumper switch of the vehicle electrical system) from the transmitter unit S, as illustrated in fig. 2. This is illustrated by the dashed double arrow of fig. 3, which corresponds in content to the curved arrow of fig. 2. The inverter Inv-stat connects the direct-voltage converter DC-stat to a (three-phase) alternating-current voltage source SQ, which may correspond in particular to a connection to a public alternating-current supply network or an alternating-current supply network.

The junction point V connects the inverter Inv-stat with the direct voltage converter DC-stat. The dc voltage converter is (at least from a logical point of view) connected to the control unit CT-stat. The control unit CT-stat is thus set up to determine the voltage at the connection point V. Furthermore, the control unit CT-stat is set up to determine the voltage at the direct voltage charging terminal DCA-stat. The control unit CT-stat is set up to determine the deviation between these voltages and to evaluate whether the deviation exceeds a predetermined value.

Fig. 1 is also used to explain another embodiment or another function of the onboard power supply system described here. In one embodiment, the vehicle electrical system FB comprises an electrical energy store 10, a dc voltage converter 20 and an inverter 30. The inverter 30 is connected to the energy store 10 via the dc voltage converter 20. The vehicle electrical system FB furthermore comprises an electric machine EM. The motor EM is connected downstream of the inverter 30. The vehicle electrical system FB furthermore has a jumper switch 40, which switchably connects the electrical energy store to the inverter 30. The electric machine is connected to the energy store via the inverter, in particular in a direct manner if the jumper switch 40 is closed, and in an indirect manner via the direct-current voltage converter 20 (also referred to as DCDC converter) if the jumper switch 40 is open.

In this further embodiment, the vehicle onboard power supply system FB comprises a control unit CT. The control unit is operatively connected to the jumper switch 40 and in particular to the dc voltage converter 20. The control unit CT may be set up to set the dc voltage converter 20 in the inactive state if the jumper switch 40 is closed and to set the dc voltage converter 20 in the active state if the jumper switch 40 is open. The control unit CT can be set up to receive the boost signal. The control unit CT can be set up to place the bridging switch 40 in the closed state if a boost signal is present. The control unit CT may be set up to place the jumper switch 40 in the open state if no boost signal is present (for example if a complementary signal with respect to this boost signal is present). The control unit may have the functions mentioned in this paragraph, as well as the functions described before or after. Alternatively, the control unit may have the functions mentioned in this paragraph and not have the functions mentioned before or after, and another control unit may be provided which has the functions mentioned before or after and not have the functions mentioned in this paragraph. The control signals of the two control units can be "or" linked in order to actuate the jumper switches in such a combination.

The control unit preferably suppresses or ignores the boost signal if the vehicle is not in a running state. If the vehicle is in a driving state, the evaluation of the voltage state of the energy store used during charging or feedback is ignored or not used to actuate the bridging switch 40. This is achieved in particular by the control unit CT.

Claims

1. A vehicle electrical system having an electrical energy store (10, 110), a direct-current voltage converter (DCDC, 20) and a direct-current transmission terminal, wherein the direct-current transmission terminal is connected to the electrical energy store (10, 110) via the direct-current voltage converter (DCDC; 20), wherein

The vehicle electrical system further has a jumper switch (40, 40') which switchably connects the electrical energy store (10, 110) to the direct voltage transmission terminal, wherein the direct voltage transmission terminal is set up for connection to a charging plug, wherein the jumper switch, when closed, bridges the direct voltage converter.

2. The vehicle electrical onboard network according to claim 1, wherein the direct voltage transmission terminal has a negative potential, which is connected to the negative terminal of the direct voltage converter (DCDC; 20), the direct voltage transmission terminal has a positive potential, which is connected to the positive terminal of the direct voltage converter (DCDC; 20), and the jumper switch (40, 40') connects the positive terminal of the direct voltage converter (DCDC; 20) to the positive pole of the electrical energy storage (10, 110).

3. The vehicle electrical system as claimed in claim 1 or 2, further comprising a control unit which is operatively connected to the jumper switch (40, 40'), wherein the control unit is connected to the electrical energy store (10) and is set up for determining a voltage state of the electrical energy store, and is connected to the dc link and is set up for determining a voltage of the dc link, wherein

The control unit is also designed to determine a deviation between the voltage state of the electrical energy store (10) and the voltage of the DC link, and to set the jumper switch in a closed state if the deviation is not greater than a predefined value, and to set the jumper switch in an open state if the deviation is greater than a predefined value.

4. The vehicle onboard power system according to claim 3, wherein the voltage state of the energy storage (10) is a value representing a terminal voltage, an idling voltage or a state of charge of the energy storage (10).

5. The vehicle electrical system as claimed in claim 3, wherein the control unit furthermore has a transmission unit which is set up to transmit the voltage state of the electrical energy store (10), the deviation or the switching state of a jumper switch (40) of the vehicle electrical system.

6. The vehicle electrical system as claimed in claim 3, wherein the predefined value is not greater than 5%, 2% or 1% of a nominal voltage of the electrical energy store (10).

7. The vehicle electrical system according to claim 3, wherein the control unit is operatively connected to the direct voltage converter (DCDC, 20) and is set up for setting the direct voltage converter in an inactive state when the bridging switch (40) is closed and in an active state when the bridging switch (40) is open.

8. Charging system having a vehicle with a vehicle electrical system according to one of claims 1 to 7 and having a charging station, wherein the charging station has a stationary inverter, stationary direct voltage charging terminals and a stationary direct voltage converter, wherein a stationary bypass switch (42) is connected in parallel with the stationary direct voltage converter, and having a stationary control unit which is connected in a controlled manner to the bypass switch (42).

9. The charging system according to claim 8, wherein the charging station has a receiving unit which is set up to receive a voltage state of the energy store (10), a deviation between the voltage state of the energy store (10) and a voltage of a direct voltage transmission terminal or a switching state of a jumper switch (40) of the vehicle electrical system.

10. The charging system according to claim 9, wherein the fixed control unit is connected to a connection point between the fixed dc voltage charging terminal and the fixed inverter and is set up to determine a voltage of the connection point, wherein the fixed control unit is further set up to determine a deviation between a voltage state of the energy store (10) and the voltage of the connection point and to set the fixed bypass switch (42) in a closed state if the deviation is not greater than a predefined value and to set the jumper switch in an open state if the deviation is greater than a predefined value.

11. A charging station has a stationary inverter, stationary DC voltage charging terminals and a stationary DC voltage converter which connects the inverter to the stationary DC voltage charging terminals, wherein a stationary bypass switch (42) is connected in parallel with the stationary DC voltage converter, and has a stationary control unit which is connected in a controlled manner to the bypass switch (42), wherein the bypass switch bridges the DC voltage converter when it is closed.

12. Charging station according to claim 11, wherein the charging station has a receiving unit which is set up to receive a voltage state of an energy store (10) of a vehicle electrical system connected to the charging station, a switching command or a switching state of a jumper switch (40) of the vehicle electrical system, wherein the receiving unit is connected to the stationary control unit and the control unit is set up to receive a voltage state of a power store of the vehicle electrical system connected to the charging station, a switching command or a switching state of a jumper switch (40) of the vehicle electrical system, wherein the receiving unit is connected to the stationary control unit and the control unit is set up to receive a voltage state of the power store of the vehicle electrical system, wherein the charging station is connected to the charging station

If the deviation of the voltage state of the electrical energy store from the voltage present between the inverter and the fixed dc voltage converter is not greater than a predefined value,

-if there is a switch command for closing the bypass switch (42), or

-if the switching state of a cross-over switch (40) of the vehicle onboard electrical system is closed,

-setting the bypass switch (42) in a closed state;

and the control unit is also designed to actuate the fixed bypass switch (42) as a function of the open switching state.

13. Method for transmitting electrical energy between an electrical energy store of a vehicle electrical system and a charging station via a direct-current voltage converter (20) of the vehicle electrical system, a stationary direct-current voltage converter of the charging station or via two direct-current voltage converters (20), wherein a direct-current voltage converter is bridged if a voltage difference between a voltage applied on a side of the voltage converter concerned facing away from the electrical energy store and a no-load voltage of the electrical energy store is below a predefined value.

14. A vehicle electrical system having an electrical energy store (10; 110), a direct-current voltage converter (DCDC; 20) and an inverter (30; WR), wherein the inverter (30; WR) is connected to the electrical energy store (10, 110) via the direct-current voltage converter (20, DCDC), wherein

The vehicle electrical system also has a jumper switch (40, 40') which switchably connects the electrical energy store (10, 110) to the inverter (30; WR), wherein the jumper switch, when closed, connects across the DC voltage converter.